js常用数组方法

1.找出数组中最大的元素

const arrayMax = arr => Math.max(...arr);
arrayMax([2,3,4]) // 4

2.数组去重

const unique = arr => [...new Set(arr)];
unique([1,2,3,1]) // [1,2,3]

3.统计重复元素出现的次数

   let count = (arr, value) => arr.reduce((a, v) => v === value ? a + 1 : a + 0, 0);
count([1,2,3,4,4,4],4)  // 3

4.拆分数组

 const chunk = (arr, size) =>
            Array.from({ length: Math.ceil(arr.length / size) }, (v, i) => arr.slice(i * size, i * size + size));
chunk([1,2,3,4,5,6,7,8],4)  // [1,2,3,4] [5,6,7,8]

 

5.数组元素相加(适用于小数，需引入bigNumber.js)

  const sum = arr => arr.reduce((pre, item) => {
            return new BigNumber(pre).plus(new BigNumber(item))
        }, 0)
console.log(sum([0.1,0.3]).toString()) // 0.4